"""
Dynamic Symbol Loader for KiCad Schematics
Loads symbols from .kicad_sym library files and injects them into schematics
on-the-fly, eliminating the need for static templates.
This enables access to all ~10,000+ KiCad symbols dynamically.
"""
import os
import uuid
import logging
from pathlib import Path
from typing import Dict, List, Optional, Tuple
import sexpdata
from sexpdata import Symbol
logger = logging.getLogger('kicad_interface')
class DynamicSymbolLoader:
"""
Dynamically loads symbols from KiCad library files and injects them into schematics
Workflow:
1. Parse .kicad_sym library file to extract symbol definition
2. Inject symbol definition into schematic's lib_symbols section
3. Create an offscreen template instance that can be cloned
4. Clone the template to create actual component instances
"""
def __init__(self):
"""Initialize the dynamic symbol loader"""
self.library_cache = {} # Cache parsed library files: path -> parsed data
self.symbol_cache = {} # Cache extracted symbols: "lib:symbol" -> symbol_def
def find_kicad_symbol_libraries(self) -> List[Path]:
"""
Find all KiCad symbol library directories
Returns:
List of paths to symbol library directories
"""
possible_paths = [
# Linux
Path("/usr/share/kicad/symbols"),
Path("/usr/local/share/kicad/symbols"),
# Windows
Path("C:/Program Files/KiCad/9.0/share/kicad/symbols"),
Path("C:/Program Files/KiCad/8.0/share/kicad/symbols"),
# macOS
Path("/Applications/KiCad/KiCad.app/Contents/SharedSupport/symbols"),
# User libraries
Path.home() / ".local" / "share" / "kicad" / "9.0" / "symbols",
Path.home() / ".local" / "share" / "kicad" / "8.0" / "symbols",
Path.home() / "Documents" / "KiCad" / "9.0" / "3rdparty" / "symbols",
]
# Check environment variables
for env_var in ['KICAD9_SYMBOL_DIR', 'KICAD8_SYMBOL_DIR', 'KICAD_SYMBOL_DIR']:
if env_var in os.environ:
possible_paths.insert(0, Path(os.environ[env_var]))
found_paths = []
for path in possible_paths:
if path.exists() and path.is_dir():
found_paths.append(path)
logger.info(f"Found KiCad symbol library directory: {path}")
return found_paths
def find_library_file(self, library_name: str) -> Optional[Path]:
"""
Find the .kicad_sym file for a given library name
Args:
library_name: Library name (e.g., "Device", "Connector_Generic")
Returns:
Path to .kicad_sym file or None if not found
"""
library_dirs = self.find_kicad_symbol_libraries()
for lib_dir in library_dirs:
lib_file = lib_dir / f"{library_name}.kicad_sym"
if lib_file.exists():
logger.debug(f"Found library file: {lib_file}")
return lib_file
logger.warning(f"Library file not found: {library_name}.kicad_sym")
return None
def parse_library_file(self, library_path: Path) -> List:
"""
Parse a .kicad_sym file into S-expression data structure
Args:
library_path: Path to .kicad_sym file
Returns:
Parsed S-expression data
"""
# Check cache first
cache_key = str(library_path)
if cache_key in self.library_cache:
logger.debug(f"Using cached library data for: {library_path.name}")
return self.library_cache[cache_key]
logger.info(f"Parsing library file: {library_path}")
try:
with open(library_path, 'r', encoding='utf-8') as f:
content = f.read()
# Parse S-expression
parsed = sexpdata.loads(content)
# Cache the result
self.library_cache[cache_key] = parsed
logger.debug(f"Successfully parsed library: {library_path.name}")
return parsed
except Exception as e:
logger.error(f"Error parsing library file {library_path}: {e}")
raise
def extract_symbol_definition(self, library_path: Path, symbol_name: str) -> Optional[List]:
"""
Extract a specific symbol definition from a library file
Args:
library_path: Path to .kicad_sym file
symbol_name: Name of symbol to extract (e.g., "R", "LED")
Returns:
Symbol definition as S-expression list, or None if not found
"""
cache_key = f"{library_path.name}:{symbol_name}"
if cache_key in self.symbol_cache:
logger.debug(f"Using cached symbol: {cache_key}")
return self.symbol_cache[cache_key]
parsed_lib = self.parse_library_file(library_path)
# Library structure: (kicad_symbol_lib (version ...) (generator ...) (symbol ...) (symbol ...) ...)
# We need to find the symbol with matching name
for item in parsed_lib:
if isinstance(item, list) and len(item) > 0:
if item[0] == Symbol('symbol'):
# Symbol structure: (symbol "Name" ...)
if len(item) > 1 and isinstance(item[1], str):
# Handle both "Device:R" and "R" formats
item_name = item[1]
if ':' in item_name:
item_name = item_name.split(':')[1]
if item_name == symbol_name:
logger.info(f"Found symbol definition: {symbol_name}")
# Cache and return
self.symbol_cache[cache_key] = item
return item
logger.warning(f"Symbol '{symbol_name}' not found in {library_path.name}")
return None
def inject_symbol_into_schematic(self, schematic_path: Path, library_name: str, symbol_name: str) -> bool:
"""
Inject a symbol definition from a library into a schematic file
Args:
schematic_path: Path to .kicad_sch file to modify
library_name: Source library name (e.g., "Device")
symbol_name: Symbol to inject (e.g., "R")
Returns:
True if successful, False otherwise
"""
try:
# 1. Find and parse the library file
library_path = self.find_library_file(library_name)
if not library_path:
raise ValueError(f"Library not found: {library_name}")
# 2. Extract the symbol definition
symbol_def = self.extract_symbol_definition(library_path, symbol_name)
if not symbol_def:
raise ValueError(f"Symbol '{symbol_name}' not found in library '{library_name}'")
# 3. Read the schematic file
with open(schematic_path, 'r', encoding='utf-8') as f:
sch_content = f.read()
sch_data = sexpdata.loads(sch_content)
# 4. Find the lib_symbols section
lib_symbols_index = None
for i, item in enumerate(sch_data):
if isinstance(item, list) and len(item) > 0 and item[0] == Symbol('lib_symbols'):
lib_symbols_index = i
break
if lib_symbols_index is None:
raise ValueError("No lib_symbols section found in schematic")
# 5. Check if symbol already exists in lib_symbols
full_symbol_name = f"{library_name}:{symbol_name}"
symbol_exists = False
for item in sch_data[lib_symbols_index][1:]: # Skip the 'lib_symbols' symbol itself
if isinstance(item, list) and len(item) > 1 and item[0] == Symbol('symbol'):
if item[1] == full_symbol_name or item[1] == symbol_name:
logger.info(f"Symbol {full_symbol_name} already exists in schematic")
symbol_exists = True
break
if not symbol_exists:
# 6. Inject the symbol definition
# Need to update the symbol name to include library prefix
modified_symbol_def = list(symbol_def) # Make a copy
modified_symbol_def[1] = full_symbol_name # Update name to "Library:Symbol"
sch_data[lib_symbols_index].append(modified_symbol_def)
logger.info(f"Injected symbol {full_symbol_name} into schematic")
# 7. Write the modified schematic back
with open(schematic_path, 'w', encoding='utf-8') as f:
output = sexpdata.dumps(sch_data)
f.write(output)
logger.info(f"Successfully injected symbol {full_symbol_name} into {schematic_path.name}")
return True
except Exception as e:
logger.error(f"Error injecting symbol into schematic: {e}")
raise
def create_template_instance(self, schematic_path: Path, library_name: str, symbol_name: str,
template_ref: Optional[str] = None) -> str:
"""
Create an offscreen template instance of a symbol that can be cloned
Args:
schematic_path: Path to .kicad_sch file
library_name: Library name (e.g., "Device")
symbol_name: Symbol name (e.g., "R")
template_ref: Optional custom reference (defaults to _TEMPLATE_{LIBRARY}_{SYMBOL})
Returns:
Template reference name
"""
try:
if template_ref is None:
# Clean up library and symbol names for reference
lib_clean = library_name.replace('-', '_').replace('.', '_')
sym_clean = symbol_name.replace('-', '_').replace('.', '_')
template_ref = f"_TEMPLATE_{lib_clean}_{sym_clean}"
# Read schematic
with open(schematic_path, 'r', encoding='utf-8') as f:
sch_content = f.read()
sch_data = sexpdata.loads(sch_content)
# Check if template already exists
for item in sch_data:
if isinstance(item, list) and len(item) > 0 and item[0] == Symbol('symbol'):
# Find Reference property
for prop in item:
if isinstance(prop, list) and len(prop) > 2 and prop[0] == Symbol('property'):
if prop[1] == "Reference" and prop[2] == template_ref:
logger.info(f"Template instance {template_ref} already exists")
return template_ref
# Find sheet_instances index (we'll insert before this)
sheet_instances_index = None
for i, item in enumerate(sch_data):
if isinstance(item, list) and len(item) > 0 and item[0] == Symbol('sheet_instances'):
sheet_instances_index = i
break
if sheet_instances_index is None:
raise ValueError("No sheet_instances section found in schematic")
# Create template symbol instance
full_lib_id = f"{library_name}:{symbol_name}"
# Calculate y position based on existing templates
template_count = sum(1 for item in sch_data if isinstance(item, list) and len(item) > 0
and item[0] == Symbol('symbol')
and any(isinstance(p, list) and len(p) > 2 and p[0] == Symbol('property')
and p[1] == "Reference" and str(p[2]).startswith('_TEMPLATE')
for p in item))
y_offset = -100 - (template_count * 10)
new_uuid = str(uuid.uuid4())
# Build the symbol instance S-expression
template_instance = [
Symbol('symbol'),
[Symbol('lib_id'), full_lib_id],
[Symbol('at'), -100, y_offset, 0],
[Symbol('unit'), 1],
[Symbol('in_bom'), Symbol('no')],
[Symbol('on_board'), Symbol('no')],
[Symbol('dnp'), Symbol('yes')],
[Symbol('uuid'), new_uuid],
[Symbol('property'), "Reference", template_ref,
[Symbol('at'), -100, y_offset - 2.54, 0],
[Symbol('effects'), [Symbol('font'), [Symbol('size'), 1.27, 1.27]]]
],
[Symbol('property'), "Value", symbol_name,
[Symbol('at'), -100, y_offset + 2.54, 0],
[Symbol('effects'), [Symbol('font'), [Symbol('size'), 1.27, 1.27]]]
],
[Symbol('property'), "Footprint", "",
[Symbol('at'), -100, y_offset, 0],
[Symbol('effects'), [Symbol('font'), [Symbol('size'), 1.27, 1.27]], Symbol('hide')]
],
[Symbol('property'), "Datasheet", "~",
[Symbol('at'), -100, y_offset, 0],
[Symbol('effects'), [Symbol('font'), [Symbol('size'), 1.27, 1.27]], Symbol('hide')]
],
]
# Insert before sheet_instances
sch_data.insert(sheet_instances_index, template_instance)
# Write back
with open(schematic_path, 'w', encoding='utf-8') as f:
output = sexpdata.dumps(sch_data)
f.write(output)
logger.info(f"Created template instance: {template_ref} at y={y_offset}")
return template_ref
except Exception as e:
logger.error(f"Error creating template instance: {e}")
raise
def load_symbol_dynamically(self, schematic_path: Path, library_name: str, symbol_name: str) -> str:
"""
Complete workflow: inject symbol and create template instance
Args:
schematic_path: Path to .kicad_sch file
library_name: Library name (e.g., "Device")
symbol_name: Symbol name (e.g., "R")
Returns:
Template reference that can be used with kicad-skip clone()
"""
logger.info(f"Loading symbol dynamically: {library_name}:{symbol_name}")
# Step 1: Inject symbol definition into lib_symbols
self.inject_symbol_into_schematic(schematic_path, library_name, symbol_name)
# Step 2: Create template instance
template_ref = self.create_template_instance(schematic_path, library_name, symbol_name)
logger.info(f"Symbol loaded successfully. Template reference: {template_ref}")
return template_ref
if __name__ == '__main__':
# Test the dynamic symbol loader
logging.basicConfig(level=logging.INFO)
loader = DynamicSymbolLoader()
print("\n=== Testing Dynamic Symbol Loader ===\n")
# Test 1: Find library directories
print("1. Finding KiCad symbol library directories...")
lib_dirs = loader.find_kicad_symbol_libraries()
print(f" Found {len(lib_dirs)} directories:")
for lib_dir in lib_dirs:
print(f" - {lib_dir}")
# Test 2: Find Device library
print("\n2. Finding Device.kicad_sym library file...")
device_lib = loader.find_library_file("Device")
if device_lib:
print(f" ✓ Found: {device_lib}")
else:
print(" ✗ Not found")
exit(1)
# Test 3: Parse library file
print("\n3. Parsing Device.kicad_sym...")
parsed = loader.parse_library_file(device_lib)
print(f" ✓ Parsed successfully ({len(parsed)} top-level items)")
# Test 4: Extract specific symbols
print("\n4. Extracting symbol definitions...")
for symbol in ['R', 'C', 'LED']:
symbol_def = loader.extract_symbol_definition(device_lib, symbol)
if symbol_def:
print(f" ✓ Extracted: {symbol}")
else:
print(f" ✗ Failed: {symbol}")
print("\n✓ All basic tests passed!")
